[2] Mills began her career as a child actress and was nominated at age 18 for a Tony Award for her stage performance in Five Finger Exercise in 1960.

[5] Because of her parents' careers, Mills grew up surrounded by famous actors, including Rex Harrison, David Niven and Marlon Brando.

She had a role in the film, The Rare Breed with James Stewart and Maureen O'Hara, and on television series such as The Man from U.N.C.L.E., Ben Casey and 12 O'Clock High.

(1972), directed by Billy Wilder, in which she starred opposite Jack Lemmon and for which she received a Golden Globe Award nomination in 1973.

[10] In 1974, Mills starred alongside fellow English actor Richard Johnson in the Italian horror film Beyond the Door, playing the role of Jessica Barrett, a woman who becomes demonically possessed after an unplanned pregnancy.

The movie was a major success, making over $15 million at the box office, though the producers were sued by Warner Bros due to similarities to The Exorcist.

Mills has stated that she herself believes in magic, witches and fairies: "There's a lot more, you know, in the aether and around us ... We have guides, and we have angels taking care of us ...

After the show was moved from a timeslot near The Partridge Family and The Brady Bunch, two highly successful sitcoms, to a different night of the week, ratings fell eventually leading to its cancellation.

Mills was the subject of This Is Your Life in 1992, when she was surprised by Michael Aspel during the curtain call of the play Fallen Angels at the Richmond Theatre.

[citation needed] In 1999, Mills was cast on the daytime drama Passions as Tabitha Lenox, a witch who was burned at the stake in the 17th century.